This deals with an automotive system that most people take for granted even though it may be the only system in your vehicle that can kill you if you don’t keep it in good repair. As you’ve probably guessed — especially titles — I’m talking about your brakes.
As with the other basic automotive systems covered, I deal with brakes in two parts: This covers the general theory behind brakes ad braking systems and tackles the hands-on information you need to repair and maintain them. Whenever you encounter a term set in this font, you’ll find it defined in the glossary in Appendix A.
One reason that today’s vehicles are the safest in history is that, since 1968, all vehicles come equipped with dual brake systems to ensure that if one set of brakes fails, the other set can still stop your car.
Your vehicle also has a dashboard light to warn you if your brakes are malfunctioning. A growing number of modern vehicles not only are equipped with hydraulic brake systems but also feature electronic brake systems that operate even more safely and efficiently.
Because electronic brake systems employ most of the same hydraulic parts as hydraulic systems, I start with the basics and get to the more advanced systems later in this chapter.
shows a basic brake system with a brake booster, disc brakes on the front wheels, and drum brakes on the rear wheels. Your vehicle may have disc brakes all around, but the principle is the same in any case.
The brake pedal
The brake pedal in your vehicle is attached to a shaft that leads to the brake master cylinder. When you step on the brake pedal, small pistons in the master cylinder force brake fluid out of the master cylinder and into the brake lines. (I tell you how to buy the proper brake fluid and work with it safely in the “Flushing and Changing Brake Fluid” section in .
If your brakes are working properly, the pedal should stop a couple of inches from the floor. It should push down easily, stop firmly at its lowest point without feeling spongy, and stay put instead of sinking down slowly when you put normal pressure on it. shows you how to check the brakes on your vehicle.
Today, most vehicles have power brakes with a brake booster located between the brake pedal and the master cylinder to increase the force applied to the pistons in the master cylinder so that your car can stop with less effort on your part .
The two most common types of power brake boosters are vacuum-assisted boosters, which use engine vacuum and atmospheric pressure to do the job; and hydraulic-assisted boosters (commonly referred to as hydro-boost units), which use hydraulic pressure from the car’s power steering to accomplish the same thing. Some vehicles with anti-lock braking systems (ABS) have a hydraulic pump to generate pressure for booster operation.
Your owner’s manual can tell you what kind(s) of brakes you have on your vehicle, in case you don’t already know, but seeing for yourself is more fun. Later in this chapter, I cover each type of brakes in detail.